TIGER Realignment
Goals
TIGER data in the US was imported in the middle of the US Census Bureau's project to correct alignments for the 2010 Census, so some counties have been greatly improved in current TIGER but have not been corrected in OSM. The idea of this import is to merge into OSM all alignment changes that have been made to TIGER and that do not conflict with edits that have been made in OSM. It should provide better geometric accuracy for huge, mostly rural, areas of the United States.
Schedule
- March, 2013: Initial investigation
- June, 2013: Talk at State of the Map US
- August, 2013: Would like to begin importing
Import Data
Background
Provide links to your sources.
Data source site: http://www2.census.gov/geo/tiger/TIGER2010/
Data license: Public Domain
OSM Data Files
http://trafficways.org/tiger/out/
Import Type
This is a one-time import. There may be a followup to add new streets that are now in TIGER but are not in OSM.
I am currently planning to upload from JOSM but scripting is probably ultimately better because of the volume of changes.
Data Preparation
Data Reduction & Simplification
Only streets that are already in OSM will be imported. Wherever possible, existing nodes will be moved instead of creating new ones. Deprecated tags will be removed from any ways that need to have nodes added or removed.
Tagging Plans
No source attributes will be imported because this import only affects alignment, not tags.
Changeset Tags
Submissions will be tagged with source=tiger_realignment
Data Transformation
The import identifies TIGER 2006 data (http://www2.census.gov/geo/tiger/tiger2006se/) that still appears in the current North American OSM extract (http://download.geofabrik.de/) and was superseded in TIGER 2010 (http://www2.census.gov/geo/tiger/TIGER2010/)
Source code is at https://github.com/ericfischer/osm-tiger-update
Data Transformation Results
http://trafficways.org/tiger/out/
Data Merge Workflow
Team Approach
I have already created the files myself. I am planning to check them in myself unless other people also want to do some of them.
Workflow
Each day of the process:
- Download an up to date OSM extract from geofabrik
- Overnight, rerun osm-tiger-update to identify the remaining TIGER changes that do not conflict with current OSM
- Submit changes for as many counties as time allows
Changeset size policy:
- Counties with over 20,000 changes are split into multiple changesets
Conflation
Only existing OSM ways are included. No portion of a way will be relocated unless its endpoints in OSM are verified by current TIGER. No midblock nodes that have been linked to other ways will be relocated.
QA
Visual spot checking during submission.